Well water, particularly water drawn from "deep" wells below thirty feet often contains high quantities of mineral derived organic dissolved solids and soluble gases, low quantities of soluble organics, and high quantities of numerous ion-complexes of the foregoing. It is not uncommon for deep water wells to contain soluble hydrogen sulfide gas, and the presence of hydrogen sulfide is serious due to the unpleasant odor, high corrosivity and toxicity.
Hydrogen sulfide concentrations within well water increase dramatically, up to five or more times normal, as atmospheric pressures decrease even as little as one percent. As the atmospheric air pressure falls, the lower level ground water at high pressure releases its higher concentrations of dissolved hydrogen sulfide which is transported to and concentrates at the higher level locations where the deep well water is removed. Accordingly, the concentration of hydrogen sulfide within well water can fluctuate widely rendering treatment difficult.
Further, due to the increasing demand for ground water the water table levels have fallen in many localities causing the hydrogen sulfide contamination to increase. Hydrogen sulfide contamination of well water is becoming increasingly prevalent. The release of hydrogen sulfide from a domestic water system can create serious human toxicity problems within confined areas such as showers and bathrooms. Even low levels of hydrogen sulfide in air reacts with copper and many other metals to corrode water pipe plumbing fixtures, electrical wiring and switches, electrical equipment and the like. The unpleasant odor of hydrogen sulfide can be detected by humans at levels as low as 0.0001 mg/l.
As the contaminants within well water vary according to locale, a variety of water processing systems are available, either for commercial or domestic use; but conventional systems will not successfully treat the broad range of specific water processing requirements needed for multiple contaminant removal, especially where the contaminant levels are high. Zeolite water softeners are widely used to control water hardness but water softeners are not effective for removing hydrogen sulfide. Potassium permanganate treated "green sand" systems are used for treating well water requiring limited oxidation treatment. While such a system can treat a higher concentration of hydrogen sulfide than a conventional zeolite water conditioning process the hydrogen sulfide treatment capacity is limited by concentrations to approximately 3.0 mg/l. Potassium permanganate is recognized as being very toxic, and, at times, it is dangerous to handle.
Chlorination systems are often employed for the treatment of well water containing hydrogen sulfide, and such systems can be effective for sulfide concentrations as high as 15 mg/l. However, the addition of chlorine to water systems can be dangerous, especially to children, and chlorine overdosing must occur to insure that stoichiometric requirements are exceeded to insure that widely varying incoming contaminant levels are fully treated. This excess chlorine must then be removed by using activated carbon filters to prevent objectionable chlorine taste and odors, and chlorine chemically combines with organic residuals of fulvic and humic acids, tannins and inorganic ions of iron and manganese to form intermediate chemical compounds which produce unacceptable odors, tastes and colors which the activated carbon filters cannot remove. The metering pumps required in a chlorine system are subjected to high rates of corrosion and require continuous maintenance and frequent replacement. While the chlorine treatment of water for hydrogen sulfide may produce a water quality satisfactory for bathing and laundry uses, it is normally considered unpotable by users.
The gas transfer process air-strips volatile gases from water using water spray aeration and fine air bubble aeration. Aeration is highly effective for removing high levels of hydrogen sulfide, but becomes increasingly ineffective at lower levels. Tests of aeration systems, such as a fine air bubble air-stripping process, show that water containing over 130 mg/l of hydrogen sulfide can be reduced to 55 mg/l within fifteen minutes. However, an additional two hours is required to reduce hydrogen sulfide to approximately 20 mg/l, and another hour is required to reach a concentration of 7.5 mg/l, and further extended aeration treatment will not lower the concentrations below 2.5 mg/l, an unacceptably high level for a domestic water system.
Ozone oxidation has been recognized as an effective water purification process and has been employed in the treatment of sulfides. Ozone has been employed in commercial and municipal high volume water treatment systems, but has not been practical for use with domestic water systems. A number of U.S. patents are directed to systems utilizing ozone in the treatment of domestic water, but the apparatus previously proposed has not been capable of effectively treating high volumes of water containing high concentrations of hydrogen sulfide ranging to 130 mg/l and higher, and prior art water treatment systems have not proven practical for various reasons. Prior art ozonization water treatment systems, like municipal systems, have all been designed to perform oxidation on a high rate stoichiometric process basis. Thus, as incoming contaminants vary widely in ozone demand requirements and water usage demands vary widely in peak-load requirements, ozone generator capacities must match or exceed these requirements if a "breakthrough" is to be prevented. Generator costs are in the range of approximately $1000.00 per ozone gram per hour output and such equipment is expensive and operating inefficiencies are numerous.
Sylva, U.S. Pat. No. 3,382,980, discloses an ozone water treating system wherein a motorized agitator is employed to intermix ozone and air with the water. This system has a low capacity of water treatment, and is expensive to operate in view of the requirement for a relatively large agitation motor.
In LaRaus, U.S. Pat. No. 3,445,001, compressed air and ozone are injected into a pressurized water tank wherein the water is treated to both ozonization and air-stripping, but as the tank is pressurized, high partial gas pressures within the tank prevent satisfactory air-stripping. The apparatus shown in this patent is not capable of effectively removing high peak-load concentrates of hydrogen sulfide at the domestic water volumes required of existing well water systems.
Hess, U.S. Pat. No. 3,448,045, discloses a water treatment system utilizing compressed air and ozone wherein treatment of the water occurs within a circuitous conduit and the treated water is stored for use as desired. Ozonization and air-stripping occurs simultaneously at the same location, and the levels of hydrogen sulfide capable of being removed are limited, and the system has a low capacity.
A two tank liquid treatment system utilizing ozone is shown in the patent to Schafer, U.S. Pat. No. 3,685,656, wherein the treatment of industrial oils is contemplated within vented tanks. The system disclosed in this patent is too complex for domestic water treatment systems.
Troglione, U.S. Pat. No. 3,784,008, discloses ozonating apparatus utilizing a vented tank. This apparatus is used to produce limited quantities of drinking water, and ozone is used for the purification treatment and treated water is removed from the treatment tank by a pump for storage within a pressurized compartment. The apparatus shown in this patent is capable of only purifying small quantities of water for drinking purposes, and is not practical for use in treating all of the water requirements of a domestic water system.